The present invention relates to the field of conductive elastomers.
Silver-containing conductive elastomers and especially silver-containing room temperature vulcanizing materials, generally known as RTVs, are used to control microwave currents for impedance matching at microwave frequencies, to shield against electromagnetic interference (EMI) and radio frequency interference (RFI) and to provide environmental seals in microwave and other electronic enclosures. The conductivity of these elastomers is provided by loading the elastomer with metal particles. The resilience of these elastomers can compensate for non-planar mating surfaces when they are used as gaskets between different portions of an enclosure to provide an environmental seal. At the same time, they provide a conductive path across the gap between the portions of an enclosure they are placed between.
Unfortunately, when silver-containing conductive elastomers are used directly against aluminum, corrosion of the aluminum results. Thus, the application of silver-containing conductive elastomer gaskets to aluminum bodies is considered a substantial reliability problem. To prevent such corrosion extraordinary measures must be taken. These measures can include coating the aluminum with silver loaded paints and epoxies, which are very expensive and whose application is labor intensive and therefore expensive as well. Another alternative is to plate the aluminum in the regions where the gasket will contact the aluminum. However, plating aluminum is in itself difficult, requires extensive surface preparation in order for the plating to properly adhere and also requires extensive masking to prevent plating portions of the aluminum where the plating is not desired. Thus, such plating is also a very labor intensive procedure. In addition, there are many instances where a gasket is required in a location where it is difficult or impossible to adequately plate or paint the mating surfaces of the aluminum. Tin-lead solder in contact with aluminum does not cause significant corrosion and is generally considered to be free of corrosion related reliability problems.
There is need for a conductive elastomer which is protected from causing corrosion of aluminum in contact therewith.